The invention relates to a method for starting a gas generation system for generating a hydrogen-containing gas for operating a fuel cell, having devices for converting starting substances into the hydrogen-containing gas, having devices for conditioning at least some of the starting substances, having devices for removing undesirable gas constituents from the hydrogen-containing gas and having a starting burner.
It is known from the general prior art that a hydrogen-containing gas can be generated by conversion of hydrocarbon-containing compounds in what are known as reformers and can be used, for example, to operate a fuel cell. In particular when fuel cells are used in motor vehicles, the hydrogen required can be generated on board from a hydrocarbon-containing compound, such as for example gasoline, diesel, naphtha, natural gas or from an alcohol, such as for example methanol. One particular requirement for all possible applications, but in particular for use in motor vehicles, is for it to be possible for the gas generation system to be started within the shortest possible time. For this purpose, in particular the components which are responsible for reforming the hydrocarbon-containing compound and for removing undesirable gas constituents from the hydrogen-containing gas have to be brought to their normal operating state as quickly as possible.
U.S. Pat. No. 4,820,594 A1 has disclosed a method for starting a gas generation system in a fuel cell system. In the starting phase of the gas generation system, the fuel which is reformed during subsequent operation in the fuel cell system is used to provide the thermal energy required to heat up the gas generation system through direct combustion of this fuel in the region of at least some components of the gas generation system. However, one drawback is that it is very difficult or even impossible to control the temperature of the thermal energy generated by the combustion. In particular when heating components with catalytically active materials, such as for example reformers, selective oxidation stages and the like, at least punctiform overheating may occur, leading to long-term damage to the catalytically active material. Moreover, a further drawback lies in the components having to be designed specially for direct heating, making it more difficult to optimize the components and if appropriate also to thermally insulate them. A further drawback which is certainly also worth noting is that the proposed starting method cannot provide for the heating of further components which require a lower temperature.
Although it would in principle be possible to devise solutions for controlling the temperature, for example by means of substoichiometric or superstoichiometric combustion, such solutions would have the drawback of very high emissions of particulates and/or unburnt residues of the fuel, and in general certainly of a hydrocarbon or the like, or of the provision of large quantities of air.
Other documents, such as for example DE 196 39 150 A1 or U.S. Pat. No. 6,268,075 B1, use catalytic burners to heat the components of the gas generation system. The drawback of such a use of catalytic burners is that only relatively low-boiling fuels can be used. The use of higher-chain and correspondingly higher-boiling hydrocarbon mixtures, such as for example diesel, is not possible or is only possible with considerable outlay for preparing the fuel prior to the actual conversion in the catalytic burners.